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CVE-2026-34742— Model Context Protocol Go SDK: DNS Rebinding Protection Disabled by Default for Servers Running on Localhost

Quick assessment

Affected
modelcontextprotocol go-sdk
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

MCP Go SDK是Model Context Protocol开源的一个模型上下文协议开发工具包。 MCP Go SDK 1.4.0之前版本存在安全漏洞，该漏洞源于默认未启用DNS重绑定保护，可能导致恶意网站绕过同源策略限制并向本地MCP服务器发送请求。

AI Predicted 4.8 Difficulty: Moderate EPSS 0.66% · P50

Possible ATT&CK Techniques 1 AI

T1565.003 · Runtime Data Manipulation

Affected Version Matrix 1

VendorProduct Version RangeStatus
modelcontextprotocol go-sdk < 1.4.0 affected
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I. Basic Information for CVE-2026-34742

Vulnerability Information
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Vulnerability Title
Model Context Protocol Go SDK: DNS Rebinding Protection Disabled by Default for Servers Running on Localhost
Source: CVE Program / CVE List V5
Vulnerability Description
The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.0, the Model Context Protocol (MCP) Go SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with StreamableHTTPHandler or SSEHandler, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. This issue has been patched in version 1.4.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
不安全的默认资源初始化
Source: CVE Program / CVE List V5
Vulnerability Title
MCP Go SDK 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MCP Go SDK是Model Context Protocol开源的一个模型上下文协议开发工具包。 MCP Go SDK 1.4.0之前版本存在安全漏洞，该漏洞源于默认未启用DNS重绑定保护，可能导致恶意网站绕过同源策略限制并向本地MCP服务器发送请求。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
modelcontextprotocol go-sdk < 1.4.0 -

II. Public POCs for CVE-2026-34742

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III. Intelligence Information for CVE-2026-34742

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Patches & Fixes for CVE-2026-34742 (3)

Vendor Advisories for CVE-2026-34742 (1)

IV. Related Vulnerabilities

Same product: go-sdk
Same vendor: modelcontextprotocol
Same weakness: CWE-1188

V. Comments for CVE-2026-34742

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